The present invention relates generally to the field of electrosurgery, and more particularly to surgical devices and methods which employ high frequency electrical energy to cut, ablate, resect, incise or otherwise remove body structures.
The field of electrosurgery includes a number of loosely related surgical techniques which have in common the application of electrical energy to modify the structure or integrity of patient tissue. Electrosurgical procedures usually operate through the application of very high frequency currents to cut or ablate tissue structures, where the operation can be monopolar or bipolar. Monopolar techniques rely on external grounding of the patient, where the surgical device defines only a single electrode pole. Bipolar devices comprise both electrodes for the application of current between their surfaces.
Electrosurgical procedures and techniques are particularly advantageous since they generally reduce patient bleeding and trauma associated with cutting operations. Current electrosurgical devices and procedures, however, suffer from a number of disadvantages. For example, conventional electrosurgical cutting devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a xe2x80x9ccutting effectxe2x80x9d along the pathway of localized tissue heating. Thus, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site.
Further, monopolar devices generally direct electric current along a defined path from the exposed or active electrode through the patient""s body to the return electrode, which is externally attached to a suitable location on the patient. This creates the potential danger that the electric current will flow through undefined paths in the patient""s body, thereby increasing the risk of unwanted electrical stimulation to portions of the patient""s body. In addition, since the defined path through the patient""s body has a relatively high impedance (because of the large distance or resistivity of the patient""s body), large voltage differences must typically be applied between the return and active electrodes in order to generate a current suitable for ablation or cutting of the target tissue. This current, however, may inadvertently flow along body paths having less impedance than the defined electrical path, which will substantially increase the current flowing through these paths, possibly causing damage to or destroying surrounding tissue.
Bipolar electrosurgical devices have an inherent advantage over monopolar devices because the return current path does not flow through the patient. In bipolar electrosurgical devices, both the active and return electrode are typically exposed so that they may both contact tissue, thereby providing a return current path from the active to the return electrode through the tissue. One drawback with this configuration, however, is that the return electrode may cause tissue desiccation or destruction at its contact point with the patient""s tissue. In addition, the active and return electrodes are typically positioned close together to ensure that the return current flows directly from the active to the return electrode. The close proximity of these electrodes generates the danger that the current will short across the electrodes, possibly impairing the electrical control system and/or damaging or destroying surrounding tissue.
The use of electrosurgical procedures (both monopolar and bipolar) in electrically conductive environments can be further problematic. For example, many arthroscopic procedures require flushing of the region to be treated with isotonic saline (also referred to as normal saline), both to maintain an isotonic environment and to keep the field of viewing clear. The presence of saline, which is a highly conductive electrolyte, can also cause shorting of the electrosurgical electrode in both monopolar and bipolar modes. Such shorting causes unnecessary heating in the treatment environment and can further cause non-specific tissue destruction.
The present invention provides systems, apparatus and methods for selectively applying electrical energy to cut or incise structures in a patient""s body. The electrosurgical systems and methods are particularly useful for removing tissue or ligaments from a patient""s joint, such as the patellar ligament in the knee, in dermatological procedures, i.e., surface treatment of the patient""s outer skin, such as the removal of pigmentations, vascular lesions (e.g., leg veins), scars, tattoos, etc., and in procedures for removing tissue in regions of the head and neck, such as UPPP procedures, tonsillectomies, adenoidectomies and the like.
In one method of the present invention, an electrosurgical probe is positioned adjacent the target tissue so that one or more electrode terminal(s) are brought into at least partial contact or close proximity with the target site in the presence of electrically conductive fluid. High frequency voltage is then applied between the electrode terminal(s) and one or more return electrode(s) and the electrode terminal(s) are translated, reciprocated or otherwise manipulated to cut through a portion of the tissue. In some embodiments, the electrically conductive fluid, e.g., isotonic saline or conductive gel, is delivered or applied to the target site to substantially surround the electrode terminal(s) with the fluid. In other embodiments, the electrode terminal(s) are immersed within the electrically conductive fluid, such as in arthroscopic procedures. In both embodiments, the high frequency voltage is preferably selected to effect a controlled depth of hemostasis of severed blood vessels within the tissue, which greatly improves the surgeon""s view of the surgical site.
In a specific configuration, the tissue is cut by molecular dissociation or disintegration processes. Conventional electrosurgery cuts through tissue by rapidly heating the tissue until cellular fluids explode, producing a cutting effect along the pathway of localized heating. The present invention volumetrically removes the tissue along the cutting pathway in a cool ablation process that minimizes thermal damage to surrounding tissue. In these embodiments, the high frequency voltage applied to the electrode terminal(s) is sufficient to vaporize an electrically conductive fluid (e.g., gel or saline) between the electrode terminal(s) and the tissue. Within the vaporized fluid, an ionized plasma is formed and charged particles (e.g., electrons) are accelerated towards the tissue to cause the molecular breakdown or disintegration of several cell layers of the tissue. This molecular dissociation is accompanied by the volumetric removal of the tissue along the pathway of tissue cutting. The short range of the accelerated charged particles within the plasma layer confines the molecular dissociation process to the cutting pathway to minimize damage and necrosis to the surrounding tissue. This process can be precisely controlled to effect the volumetric removal of tissue as thin as 10 to 150 microns with minimal heating of, or damage to, surrounding or underlying tissue structures. A more complete description of this phenomena is described in commonly assigned U.S. Pat. No. 5,683,366, the complete disclosure of which is incorporated herein by reference.
In an exemplary embodiment, a method for removing a ligament from a joint, e.g., the patellar ligament or a cruciate ligament from the knee, includes positioning the electrosurgical probe adjacent the ligament and applying high frequency electrical energy between one or more electrode terminal(s) and one or more return electrode(s) in the presence of electrically conductive fluid. The probe is then translated so that the electrode terminal(s) volumetrically remove ligament tissue along the cutting path. In an exemplary embodiment, two spaced electrode terminals on the distal end of the probe are positioned on either side of the ligament. The probe is advanced along the length of the ligament while high frequency electrical energy is applied between the electrode terminal(s) and a return electrode to remove or cut the tissue or other structures surrounding the ligament. The residual heat from the electrical energy also provides simultaneous hemostasis of severed blood vessels, which increases visualization and improves recovery time for the patient. In addition, the ability to simultaneously cut through tissue on either side of the ligament decreases the length of the procedure, which further improves patient recovery time. The ligament is then removed by severing the upper and lower portions and removing the central portion of the ligament from the joint either with a conventional scalpel or with one of the electrosurgical scalpels of the present invention.
Apparatus according to the present invention generally include an electrosurgical instrument, such as a probe or catheter, having a shaft with proximal and distal ends, one or more electrode terminal(s) at the distal end and one or more connectors coupling the electrode terminal(s) to a source of high frequency electrical energy. The electrode terminal(s) are preferably designed for cutting tissue; i.e., they typically have a distal edge or point. In the exemplary embodiment, the electrode terminal(s) are aligned with each other to form a linear cutting path through the tissue.
The apparatus preferably further includes a fluid delivery element for delivering electrically conducting fluid to the electrode terminal(s) and the target site. The fluid delivery element may be located on the probe, e.g., a fluid lumen or tube, or it may be part of a separate instrument. Alternatively, an electrically conducting gel or spray, such as a saline electrolyte or other conductive gel, may be applied the target site. In this embodiment, the apparatus may not have a fluid delivery element. In both embodiments, the electrically conducting fluid preferably generates a current flow path between the electrode terminal(s) and one or more return electrode(s). In an exemplary embodiment, the return electrode is located on the probe and spaced a sufficient distance from the electrode terminal(s) to substantially avoid or minimize current shorting therebetween and to shield the return electrode from tissue at the target site.
In a specific configuration, the electrosurgical probe includes an electrically insulating electrode support member having a tissue treatment surface at the distal end of the probe. One or more electrode terminal(s) are coupled to, or integral with, the electrode support member such that the electrode terminal(s) are spaced from the return electrode. In one embodiment, the probe includes a plurality of electrode terminal(s) having distal edges linearly aligned with each other to form a sharp cutting path for cutting tissue. The electrode terminals are preferably electrically isolated from each other, and they extend about 0.2 mm to about 10 mm distally from the tissue treatment surface of the electrode support member. In this embodiment, the probe may further include one or more lumens for delivering electrically conductive fluid to one or more openings around the tissue treatment surface of the electrode support member. In an exemplary embodiment, the lumen extends through a fluid tube exterior to the probe shaft that ends proximal to the return electrode.
In another aspect of the invention, the electrode support member comprises a plurality of wafer layers bonded together, e.g., by a glass adhesive or the like. The wafer layers each have conductive strips plated or printed thereon to form the electrode terminal(s) and the return electrode(s). In one embodiment, the proximal end of the wafer layers will have a number of holes extending from the conductor strips to an exposed surface of the wafer layers for connection to electrical conductor lead traces in the electrosurgical probe or handpiece. The wafer layers preferably comprise a ceramic material, such as alumina, and the electrode will preferably comprise a metallic material, such as gold, platinum, tungsten, palladium, silver or the like.